Traditionally, in the field of multi function peripherals having a FAX function, there is a technique disclosed in Japanese Patent No. 4204739. In a multi function peripheral according to Japanese Patent No. 4204739, when an abnormity is detected in the toner density by a toner density sensor detecting the toner density in a developing unit, received FAX image data is stored into a storage section. Then, the stored FAX image data is outputted by an image forming section, and then a message requesting a check whether the output has been normal is displayed on a display section. Then, when a user inputs confirmation of normal output through an operation section, the multi function peripheral deletes the FAX image data stored in the storage section because the data is no longer necessary. In contrast, in case of abnormal output, the FAX image data is held in the storage section.